Boiler feed water regulating apparatus



March 19; 1935. J. M. BARRETT 1,995,237

BOILER FEED WATER REGULATING APPARATUS Filed 6, 1930 2 Sheets-Sheet lFIG.1

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INVENTOR Jo eph M Barrett,

4am M A TORNEY March 19, 1935.

STEAM FLOW WATER FLOW J. M. BARRETT BOILER FEED WATER REGULATINGAPPARATUS Filed Aug. 6, 1930 FIGS PRESSURE DROP THROUGH SUPERH EATERDIFFERENTIAL PRESSURE PRESSURE DROP THROUGH SUPERHEATER STEAM FLOWACROSS REGULATOR H DIFFERENTIAL PRESSURE ACROSS REGULATOR H WATER FLOWPOSITION 2 Sheets-Sheet 2 VALVE STEM PASSAGE AREA WATER FLOW PASSAGEAREA VALVE STEM POSITION WATER FLOW INVENTOR' I JOSeph M B arrect.

ATTORNEY Patented Mar. 19, 1935 UNITED STATES a g tnszii BOILER FEEDWATER REGULATING I APPARATUS Joseph M. Barrett, Cleveland Heights, Ohio,as-

signor to Bailey Meter Company, a corporation of Delaware ApplicationAugust 6, 1930, seem No. 473,459

6 Claims. (01. 122 -4512) This invention relates to: regulatingapparatus for. the feeding of water to steam generating boilers, and inparticular to provide an arrangement whereby water will be fed to theboiler at thepropei rate for efficient and safe operation.

Such boilers commonly have one or more drums in an upper partof theassembly, for water storage. One or more of. these drums are usuallyonly partly filled with water, thus providing a steam liberatingsurface. To the steam space so formed, the steam outlet pipe isconnected, and it is important that the level of water be so maintainedthat with steam leaving the boiler at high velocities, water is not carI ried out in slugs or otherwise with thesteam.

It is equally important that the level be not lowered to a point whereburning of the parts would occur due to being exposed to hightcmperatures without heat conducting liquid on the other side of themetal.

For a definite weight of water in the boiler the location in elevationof the steam liberating surface, commonly termed the drum level, willvary widely with changes in rating due to swell. or the efiect of thepercentage of'steam bubbles below the surface of the water. Immediatelyupon an increase in rate of steam generation the Water in the boilerwill swell up, raising the drum level appreciably, and it has beenalmost universally the operation of feed water regulators to immediatelypinch down on the rate of feed until the increased rate of evaporationin the boiler has-used water from, the storage total to an extent thatthe level'within the drum drops from its. swelled position not only toits ori inal level but to a lower level corresponding to the new rate ofsteam generation, sufficient to open up the feed water regu-i lator anamount whereby water will be supplied at a rate corresponding to the newrate of output.

By so allowing the water in the boiler drum to evaporate down to aminimum level before the feed water regulator opens further and admitswater at a rate commensuratewith the new rate of steam generation, a lagin water inflow compared to steam outflow is introduced which isofttimes serious considering the small storage available for water. Highpressure design dictates from a cost standpoint the use of small waterstorage drums containing possimy only if) to 20% of the total water ofthe boil er. Such conditions mean that at a high rate of steamgeneration the water stored in the boiler drum is sui'ficient to lastonlyfa minute or a fraction thereof, so that if the feed of wa-I ter tothe boiler'is interrupted or not in step with changes in steam output,the water stored in the drum will be used up and serious damage mightresult. j v

, The primary object of my invention is to provide an improvedconstruction and arrangement for controlling the supply of feed water.to a boiler whereby the supply is controlled from factors indicative ofthe usage and of the total weight or mass of water in the boiler, ratherthan from factors indicative of. drum level, which as pointed out above,is affected not only by usage but also by swell. I

A "further object of my invention is to maintain the level ofwater inthe boiler drum within safe limits while allowing it to vary withvarying rates of operation.

Another object is to provide means for feeding water to the boilerinaccordancewith the usage," to keep a definite weight of water intheboilen Other objects of the invention-are ob- J vious and in part willappearmore in detail from the descriptionv hereinafter. In .the drawingsFig; 1 represents {diagrammatically one arrangement offee'd waterregulating apparatus embodying the invention:""

Fig. 2 is a sectional'view of part ofa regulat= ingvalva- 3 Figs. 3m 9inclusive represent graphically, re-

lations between various wfactorsin my invention."

.Referring to the drawings, 1 indicates conventionally a steam boiler.comprising-upper andlower drums connected by ,boiler tubesda.. Connected to an upper drumis-a conduit which leads through a superheatertto a discharge conduit 4, and connected 'to an'upper drum is a feed.water supply conduit "2. Conduit 2 is shown in part on a large scale inorder to illustrate better the con; struction of certain parts; Thestructure so far described is to 'be taken as typical of any suitableboiler structure. r

' In the embodiment being described, is-illustrated a valve meanslocated in the conduit'2 controlling the admission of water to theboiler varying with rate of steam generation in the boiler, which for aconstant opening of the flow regulating valve, results in an admissionof water to the boiler directly proportional to the rate of steamgeneration. However, due to leakage or other causes, the weight of waterin the boiler may gradually increase or decrease, and I readjust theamount of opening of the flow regulating valve to compensate for thechange in weight of water in the boiler.

As an indication of variation in the total weight of water in theboiler, I have found that the level in a cold water leg of a U-tube, ofwhich the boiler proper forms the hot water or other leg, is the mostsatisfactory. Referring to Fig. 1, the pipe 6, external to the boiler,is connected to the lowest chamber of the boiler and by the joining pipe'7, to the steam space of an upper drum. A U-tube joined at the upperends on account of the pressure in the boiler, is thus formed. The levelof water within the boiler, indicated at A, is subject to swell,ebullition and entirely different temperature-density conditions than isthe level indicated at B, in the communicating pipes 6 and '7 externalto the boiler. Normally the water level B is lower than the level A,except when the boiler is cold, at which time the temperatures'beinguniform throughout the system, levels A and B will be the same. Waterlevel B is unafiected by swell, varies only with usage, and is thereforeindicative of'the weight of water in the boiler as a whole.

As a means of operating the flow regulating valve 11, responsive tovariations in the. .water level B, indicative of weight of water in theboiler,

I employ a trapped vapor-generating system, comprising a generatorindicated generally at 5, connected by a pipe 1'7 to an expansible metalbellows 16 mounted on the valve 11, in a manner to position thevalveparts and regulatethe passage area for flow through the valve-. Thegenerator comprises a pipe 8 joined to and in communication withthepiped, lying across or spanning inclinably thenormal water level B inthe pipe 6, and surrounded by J a trapped annular chamber 9a'as enclosedby av pipe 9 provided with fins for heat radiation. and closed at theends by flanges 10. The trapped chamber 9a contains a vaporableliquidsuch as water in contact or suit- ,able heat-conducting relation withpipe 8 which has normally awater level B corresponding with the waterlevel in pipe 6.

- Steam in the pipe 8 above the water level B, by heat transfercauses avaporizing of someof the liquid in the chamber. 911-, creating apressure effective upon the remainder of the liquid in the chamber 9aacting upon the expansiblemetal bellows 16 through the connecting pipe17. A state of equilibrium is reached in the trapped generating systemwhen the level of liquid within the annular chamber 9a corresponds tothe level in'the pipe 8, through vaporization, and the resultingpressure having transferred some of the trapped liquid to the expansiblemetal bellows 16, causes a movement of its abutment 15, which movementis resisted by a spring 14.

To the movable abutment 15 of the motive bellows 16 is connectedthe'valve stem 13- and movement of the abutment results in movement ofthe valve stem 13 to vary the passage opening through the valve 11. Thepassage area for flow through the valve 11 is thus varied in accordancewith variations in a water level existing in the pipe 6, indicativeofthe weight of water in theboiler.

To control the pressure of the water entering the flow regulating valve11, I provide a valve means 12 located in the conduit 2 at the inlet tothe valve 11. The pressure of the water entering the valve 11 iscontrolled through the throttling action of valve discs fastened to astem 18 and positioned relative to their seats in the valve 12. The stem18 is fastened to and operated by a piston 20 movable in a suitablecylinder part of the valve 12, the piston 20 being subjected to thepressure of the water at the inlet to valve 11 on its upper side and thepressure existing in the boiler 1 on its lower side. To transmit to thepiston 20 a pressure representative of that in the boiler 1, is shown apipe 21 connected by the pipe 7 to an upper drum of the boiler, andhaving a condensation chamber 22 located at the highest point ofconnection so as to provide a definite static water head.

It is necessary that the pressure of the water entering the valve 11 begreater than the pressure in the boiler, otherwise water would not enterthe boiler. Furthermore, some frictional loss of pressure will occur inthe passage of'the water through the passage-area of the valve 11.

' To control the pressure of the water entering the valve 11, a spring19 is provided, acting against a lever support 27 at the one. end andeffective on the stem 18 at the other end to urge the stem and valvediscs away from the valve seats, in the same direction of force as-theboiler pressiu'e acts on the piston 20. For a fixed position of thelever support 2'7, the valve discs are urged away from their seats bythe effect of the spring 19 plus the force of the boiler pressure on thepiston 20, and are urged toward their seats by the force of the waterpressure at the outlet of the valve, acting on the other side of thepiston 20. The spring 19 then forms a .calibrating measure of thepressure differential which will exist between the pressure in theboiler and the pressure of the water entering valve 11, the tendencybeing toalways supply water at a constant excess over boiler pressure.

In order that the feedof water to the boiler shall be directlyproportional to the rate of steam generation or boiler output I providein connection with the valve means 12, a further arrangement of parts,responsive to a function of boiler output, for varying the efiect of thespring 19 and correspondingly Varying the excess of pressure of thewater entering the valve 11 over the pressure in the boiler.

To vary the effect'of the spring 19 is provided a means for moving itssupport, namely the lever 27, so that for any given position of thevalve stem 18, the spring will be moreor less compressed and exert agreater or lesser force tending to move the valve stem. The lever 27 ispivoted between its ends and at'the end opposite that supporting thespring 19, is connected to a rod .26, having an adjustment, illustratedas a turnbuckle 29, for length. To the lower end of the rod. 26 isfastened themovable abutment 25 of an expansible metal bellows 24 whichis sub.-

jected to a pressure differential varying in a known manner with rate ofsteam generation.

The pressure which is eifective on the outside of the bellows 24 is thatof theboiler 1 transmitted through the pipes '7 and 21, while thateffective on the inside of the bellows 24 is that of the steam outletconduit 4, transmitted through the pipe 23. The difference between thesetwo pressures is that lost by the steam in its passage from the boilerdrums, through the superheater' 3 to the outlet conduit 4 andthispressure loss or differential varies in a known manner with rate ofsteam flow. The pressure difierentialefiective upon the bellows 24 andupon the loading of the spring 19 bears, then, a definite relation toboiler output. s j

For the valve means 12 I have provided various adjustments to take careof changes in operating orother conditions. At 28 is indicated a stopthreaded through the casing, providing an adjustable limit to the travelof the piston and through the stem 18 of the valve discs relative totheir seats. By adjustment of the screw 28 upwardly toward the piston 20the travel of the piston will be so limited in the one direction thatthe valve may have any desired minimum opening to protect againstcompletely shutting 01f the flow of water supplying the valvell.Adjustable means indicated at 29as aturnbuckle may be used to varythelength of the rod 26 and change the initial loading of the spring 19and correspondingly the effect of the function of boiler output upon theloading. of the-spring 19. At 30 I have indicated a stop threadedthrough the casing, adjustable to limit the travel of lever 27 wherebythe minimum loading of the spring 19 may be varied. v

The movable abutment of the bellows 24 is mechanically limited in itstravel in an upward direction by the casing of the pressure differentialvalve 12 and in a downward direction by a stop 31. The hand adjustmentillustrated at 29 as a turn buckle then serves to shorten or lengthenthe connecting link 26, thereby increasing or decreasing the compressionof the spring 19 and correspondingly loading or unloading thedifferential pressure valve 12. By this means a limit may be set to thelowest excess pressure which can exist across the two sides ofregulating valve 11.

The adjustable stop 28 not only provides for limiting the travel of thevalve stem 18 in a manner such that the valve can never be closed belowa predetermined amount as controlled by the position of thestop28,butalso provides a hand means of opening the valve to any desired positionregardless of pressure conditions throughout the system. The valves onstem 18 are permittedto seat and close off, if the adjustable stop 28 isY backed downwardly out of the way. The adjust able stop acting againstthe lever 2'? provides a means for limiting the unloading effect on thespring 19 and providing hand adjustment below the limit encountered whenthe movable abut-i ment 25 ofthe bellows24-comes against the cas ing'ofthe pressure valve 12.

I have described in detail the component parts and mechanismsillustrated in Fig. 1 and in accordance with the present embodiment ofmyinvention they are preferably located indefinite re-' lation to eachother and the boiler. For instance, I prefer to locate the pressurecontrol valve 12 in the conduit 2 at the inlet side of the flowregulating valve .11. I have shown anddescribed the spring 19 of thevalve means'12 as being located 1 in accordance with a pressuredifferential which is obtained across the superheater 3 but I mightequally as well insert an orifice or other pressure differentialproducing device in the conduit 4. Likewise, the generator 5 is. shownat a certain inclination across the water level 13 in the pipe 6 whereasit might under certain conditions be desirable to incline it more orless or move it up or down relative to the pipe 6. I

The relation (due to swell) between the water level Aandi the rate ofsteam generation, assuming a constant weight of water in the boiler, isapproximately'parabolic in function. The actual location in elevationand inclination ofthe generator 5 across the level B isdetermined by thelimitations of drum size and allowable or desirable change in the level'A with variations in rat of steam generation. I

It may be desirable to allow a relatively low level A to exist at lowrates of steam output'so that upon a sudden or appreciable increase inthe rate of output the level will not go to a dangerous height andconversely, to have a high level A at high rates of steam output so thatupon a sudden and appreciable decrease, in rate of output, the levelwill not fall to a dangerous low point.

The feed water regulators now common in which the valve is positionedfrom level A affected by swell, are in effect geared to level. That is,there is a definite level A and a definite valve position for each rateof steam generation,

and not only will these levels vary with a dif-.-

ferent excesspressure across the valve opening, but for equal incrementsof rate of steam. generation, there will be unequal increments of changein level'A due to the characteristic of the swell relation. Further,equal increments of valve stem travel may not result in equal incrementsof flow of water through the valve.

With my invention I provide for the feeding of water to the boiler inaccordance with the usage, and tending to keep a definite weight ofwater in the boiler. My invention is responsive to variations in a levelwhich is unaffected by swell, and to a factor indicative'of rate ofusage.

In operation, assumea definite rate of steam generation in which, forexample, level A exists approximately at the center line of the drum asshown, and level 13 at the centerline of" the in clined generator 5. Theflow regulating'valve l1 and the pressure controlling valve 12 have acertain assumed open position, and water is being fed to the boiler. Iwill now describe the effect of an increase'in the rate of steamgeneration or.

however, unaffected by swell and varies only as r the total weightofwater in the boiler changes from discrepancy between inputand output, or

from losses such as blowdown, blowing of the safety valves, leakage,etc.

I have in the flow regulating valve 11 two variables responsible forchanges in the rate of feed of Water to the boiler, first thepassage-area, and second the differential pressure impressed across thevalve, resulting in flow through the passagearea." I

The first is controlled or varied-by movement of the valve stem 13in-accordance with changes in level B indicative of weight of water-inthe boiler, or discrepancy between input and output.

An important. feature of my'invention is that I different sizes ordesigns of valves. I may if desired so shape the ports or passages thatthe rela tion between equal increments of valve stem motion andincrements of flow may be direct, verse, or as any desired function.

Cal

In Fig. 9 I have plotted a straight line "relation between valve'stemposition and water flow, the relation which exists in the preferred formof my invention wherein-equal increments of movement of the stem 13 ofthe regulating valve 11 result in equal increments of water flow for agiven excess pressure across thevalve 11. This is accomplished by soshaping the ports or passages 11a that a relation asshown in Fig. 7between valve stem position and passage-area will result in the relationshown in Fig. 8 between water flow and passage-area, in turn giving thestraight line relation of Fig. 9. The curves Fig. 7 and Fig. 8 are drawnof arbitrary shape and are preferably obtained by experiment. The curveof Fig. 9 results from those of Fig. '7 and Fig. 8 as Figs. 7 and 8 areof the same shape and incremental value.

The second variable, the excess pressure, I control to give a flow ofwater directly proportional to the rate of steamgeneration or boileroutput. For a given passage-area the water flow will vary directly asthe square root of the excess pressure across the regulating valve 11.The excess pressure is controlled directly by the loading of the spring19 through the action of the expansible metal bellows 24 acted upon bythe differential pressure or drop in pressure of the steam flowingthrough the superheater 3. This differential pressure varies as thesquare of the rate of steam flow so that water flow (for anygivenpassage-area in the regulating valve 11) will be directlyproportional to the rate of steam output.

In Fig. 3 I have plotted the relation existing 1 between flow andpressure drop, in which the rate of flow of steam through thesuperheater varies as the square root of the pressure drop. Fig. 4 is asimilar curve of the relation existing across the regulating valve llfor a given passage-area in which the rate of flow of water through thegiven passage-area varies as the square root of the excess pressureacross said passage-area.

Inasmuch as the pressure drop through the superheater is applied throughthe bellows 2 4, the movable abutment 25, link 26 and lever 27 to loadthe spring 19 which is coactingiwith the piston 20 in positioning thevalve discs relative to v their seats in the pressure'controlling valve12 to control the pressure of water at the inlet to the regulating valve11 relative to boiler pressure atthe outlet side of the regulating valve11, and

thus control the differential pressure across the given passage-areain-regulating valve 11, then the relationexisting;v between pressuredrop through the superheater and the differential pressure across theregulating valve as plotted in Fig.5 as a straight line holds true.

With the differential pressure across the regulating valve 11 directlyproportional to the pressure drop, through the superheater, which inturn varies as the square of the rate of steam flow and itself varies asthe square of the rate of water flow, then the relation between steamflow and water flow as plotted in Fig. 6 is astraight line.

I have then a regulating valve 11 through which the flow of water willvary directly in accordance with changes in weight of water in theboiler as well as directly with the rate of steam genera tion.

If then the rate of steam output is increased there will be an immediatechange in the rate of feed of Water to the boiler through a change inexcess pressure. The increased flow of steam through superheater 3 willresult inv a change in the pressure drop, and this will be reflectedthrough conduits '7 and 21 to one side of the bellows 24 and throughconduit 23 to the other side of the bellows 24, causing a change in thepositionv of the movable abutment 25 which through the intermediary ofthe rod 26 and the fulcrumed' lever 27 varies the loading on .the spring19 resulting in a change in the pressure of the water at the inlet tothe regulating valve 11 relative to the pressure in the boiler 1 on theoutlet side of the regulating valve 11. As explained before, the flowthrough the fixed passage-area of the regulating valve 11 will varydirectly with the change in the rate of steam generation.

Now assuming that leakage or discrepancy be tween the input and outflowresults in a change in the weight of Water in the boiler, this will bereflected by a change in the level B in the intercommunicating conduitsystem comprising conduits 7, 8 and 6. With the level B in conduit 8gradually sinking, for, example, through the using up of stored water, agreater steam zone comes in contact with the liquid trapped in chamber9a, additional liquid is vaporized and the increase in pressure sogenerated acting through the connecting conduit 17 on the bellows 16operates to open the regulating valve 11 somewhat or change itspassage-area. Inasmuch as the valve ports or openings are in thisembodiment so designed that equal increments of valve stem travel willresult inequal increments of flow, then for a constant differentialpressure across the passage-area an increased flow of water will result,directly proportional to variations in. the level B which is indicativeof changes in the weight of water in the boiler as a whole.

I have then to all intents and purposes a regulating apparatus which-isresponsive to a level unaffected by swell for obtainingzthe valveopening, and at said valve opening has impressed upon it a pressuredifferential varying as a function of the rate of steam generation orboiler output, controlling to maintain a definite weightof water in theboiler system.

I have illustrated and described one embodiment of my invention, but itis expressly understood that by so doing I have not limited my inventionother than, as stated in the claims in view of prior art.

'WhatI claim as new and desire tosecure by Letters Patent of the UnitedStates, is:-

1. In combination, .a boiler, a conduit for supplying liquid to theboiler, a conduit through which vapor is discharged from the boiler, avalve in the supply conduit, means responsive to variations in anindication of the weight. of water in the boiler for positioning saidvalve, a second valve in said conduit in advance of said first-namedvalve, and means responsive to the rate of flow of vapor from. theboiler for positioning. said second-named valve, said second-named valvecontrolling the pressure at the inlet to the firstnamedvalve'proportional to a function of the saidrate of flow of vapor.

2. A boiler, a feed water regulator, a generator controller thereforcomprising a conduit connected to and. spanning in elevation the entireboiler and a trapped'generator chamber containing a vaporable liquidlocated to be responsive to variations in an indication of the weight ofwater. in the boiler, and means responsive to a function of boileroutput to vary the pressure diiferential across said regulator. 3. 'Incombination, a boiler, a feed water regulator therefor, controlmeans forsaid regulator responsive to variations in an indication of the weightof water in the boiler, and means responsive to the rate of flow ofsteam from said boiler to vary the pressure of the water supplied tosaid regulator. r

4. A boiler, a feed water regulator, a controller therefor responsive tovariations in the weight of water in the boiler, and means responsive toa function of boiler output to vary the pressure differential acrosssaid regulator.

5. In a boiler feed water regulator, means responsive to Variations inthe weight of water in the boiler for varying the passage-area of theregulator, and means responsive to a function of steam outflow to varythe pressure differential across said regulator.

6. A boiler, a feed water regulator therefor having means for varyingthe area of the flow passages therethrough, said means responsive tovariations in the weight of water in the boiler, the flow passages soproportioned as to result in a definite relation between incrementsof'regulat JOSEPH M. BARRETT.

